1). Field of the Invention
This invention relates generally to the fabrication of semiconductor devices and particularly to a method of striping photoresist from a passivation layer over metal lines and more particularly to a F-containing gas passivation treatment of bonding pad after a dry etch of a passivation layer overlying the bonding pad.
2). Description of the Prior Art
This invention relates to the prevention of metal corrosion after dry etches. Two manufacturing processes which have metal corrosion problems are the patterning of passivation layers over bonding pad formations and the patterning of metal lines. These two problems are explained below.
First, metal bonds are formed to metal bonding pads in a top metal layer on a semiconductor chip. This occurs after the chip has completed the fabrication process. It is usually assembled into a package to be utilized on a printed circuit board as part of a larger circuit. In order for the inner leads of the package to make electrical contact with the bonding pads of the chip, a metal bond is formed at the bonding pad of the chip with a lead extending to the inner lead of the package lead frame.
FIGS. 1A and 1B show a conventional bond pad area. A top metal layer 118 is formed over a top dielectric layer over a semiconductor substrate 110. The top metal layer is then etched to form metal lines. Bonding pad areas 124 are then etched into the top metal layer using conventional photolithographic processes. A passivation layer 122 is formed over a top metal layer 118. The passivation layer 122 can be formed of silicon oxide. The passivation layer is patterned using a photolithography and a dry etch process to form an opening over the bond pad area 124. We have encountered a corrosion problem of the top metal layer 188 in the bonding pad area after the dry etch of the passivation layer 122. Next, a metal bond is formed in the bonding pad area. The metal corrosion creates fails.
Second, another corrosion problem occurs when patterning metal lines after an etch. A conventional method of making wiring layer for VLSI devices or the like is shown in FIG. 2 is known. An aluminum (Al) based wiring material layer, i.e. Al or Al alloy is deposited on an insulating film 112 covering the surface of a semiconductor substrate 110. Thereafter, a resist layer 16 is formed thereon and patterned in a desired layout. Using the resist layer 116 as a mask, the Al based wiring material layer is selectively etched by using a Cl based gas.
Thereafter, the resist layer 16 and etch by-products generated during the etching process are removed. Normally, an dry ashing process is used. The ashing process is performed using under plasma assisted conditions where an oxygen radical generated in the plasma reacts with organic material included in the resist materials. Thereby, the resist materials are oxidized and resolved. The photoresist removal process has been performed by two methods. First, photoresist ashing removal process is performed by an ashing process using a mixed gas of a fluorine (F) containing gas and an O.sub.2 gas. The second method performed the ashing by using a plasma of a mixed gas, which contains hydrogen and oxygen (a H and O containing gas), such as CH.sub.3 OH and an O.sub.2 gas.
The first process (F and O.sub.2) cannot remove Cl components sufficiently, which have attached during the etching process on the surface of the wafer. The unremoved Cl components may corrode a wiring. For a laminated layer having a barrier metal layer, such as TiW under the Al based wiring material layer, there are not only unremoved Cl components but also local batteries formed by the layers. This corrosion can more likely occur.
The second process (H.sub.2 O) is an improved version of the first process. With the second method, however, it is necessary to heat a substrate or wafer to about 250 to 350.degree. C. in order to obtain a practical ashing speed. This heating process alters the quality of and cures, the resist surface in which the etching gas and by-product (such as AlCl.sub.x, CuCl.sub.2, SiCl.sub.x) have been mixed. As shown in FIG. 2, resist surface layers of the resist film 116, particularly resist surface layer 116A and 116B, which are sometimes called rabbit ears, may be left unremoved.
Although the resist surface layers 116A and 116B may also be left unremoved when using the first method, theses layers can be readily washed out by amine based solvent. However, with the second method, the quality change and curing of the resist surface layer reached sometimes to the extent that the surface layer cannot be removed even if it is processed by amine based solvent, thereby lowering the manufacturing yield.
Others have attempted to solve aluminum corrosion problems after etching Al lines. The most pertinent appear to be, U.S. Pat. No. 5,202,291 (Charvat et al.) teaches a method of etching Al using a high CF.sub.4 RIE. The patent shows the replacement of Cl with a carbonaceous species. U.S. Pat. No. 5,468,686 (Kawamoto) teaches a method of etching aluminum on a wafer with a Halogen gas and then cleaning the wafer and chamber with an oxygen containing gas. U.S. Pat. No. 5,451,293 (Tabara) teaches a method of ashing a photoresist layer using H and O containing gas with a F containing gas. U.S. Pat. No. 5,378,653(Yanagida) and U.S. Pat. No. 5,399,236 (Ha et al) show methods of reducing aluminum corrosion caused by Cl.sub.2.